Apparatus for making formed fibrous webs



1966 PER BORJE WAHLSTRCM 3,236,724

APPARATUS FOR MAKING FORMED FIBHOUS WEBS Filed Nov. 23, 1962 INVENTOR PER BGRJE wAHLsTRM HIS ATTORNEYS 3,236,724 APPARATUS FOR MAKING FORMED FIEROUS WEBS Per Biirje Wahlstriirn, Karlstad, Sweden, assignor to Aktieholaget Karllstads Mekaniska Werkstad, Karlstad, Sweden, a company of Sweden Fiied Nov. 23, 1962, Ser. No. 239,641

Claims priority, application Sweden, Nov. 25, 1961,

11,749/ 61 6 Claims. (Cl. 162317) The present invention relates to methods and apparatus for the forming of a fibrous web from fibres in a liquid suspension. The invention is particularly characterized by the feeding of a fibre suspension under hydro-static pressure into an opening between a felt running along a suitably perforated, rotating drum and a wire screen running over a part of the periphery of the same drum whereby the space between the felt and the wire at the principal concave part of the wire screen loop along the drum is determined solely by the tension of the wire and the resistance to compression of the fibre suspension or the web wit-h its varying degree of moisture. This causes an effective drainage of the web as the wire automatically adjusts itself to such a position that it exerts a maximum and even pressure on the web along its entire pass. It is advantageous to use an endless fine mesh e.g. of plastic in direct contact with the web and to support this mesh by another endless mesh of a coarser and stronger type e.g. a wire screen of metal which can withstand a high tension and transfer a high drainage pressure to the web.

The invention also relates to a paper making machine for practising the above method.

An exemplary embodiment of the invention will be described With reference to the attached drawing which schematically shows a paper making machine according to the invention.

The drawing shows the perforated cylindrical periphery 11 of a driven drum 12 or roll with a horizontal shaft 13. An endless felt 15, is mounted so as to envelop the drum 12 contacting the lower part of the perforated periphery 11 and forming an upper loop passing through a felt washing arrangement 21. Below the drum 12 an endless wire 23 forms a loop around the guide rolls 25, 27, 29 and 32 of which one, e.g. roll 27 preferably is driven. A tension roll 31 is vertically adjustable for obtaining a suitable tension of the wire. The guide rolls 25 and 27 are located on opposite sides of the lower part of the drum 12 and approximately on the same level so that about one third of the periphery 11 of the drum 12 projects downwards between the two rolls 25 and 27. The roll 27 may be in contact with the drum 12, but the roll 25 will be kept at an adjustable distance from the drum. In the opening 33 between the drum 12 and the roll 25 a slot formed nozzle 35, extending over practically the whole axial length of the drum 12 and the roll 25, is arranged for the supply of the fibre suspension to form the web 53. The upper part of the nozzle 35 may be sealed against the felt and the lower part of the nozzle 35 sealed against the wire 23 so as to maintain the hydro static pressure of the fibre suspension, delivered through the nozzle 35 to the gap 33. The hydrostatic pressure will make the wire 23 form an arc converging towards the periphery 11 of the drum 12 from the roll to the roll 27. The fibre suspension fed into the space between the wire 23 and the felt 15 will be rapidly and efliciently drained under the pressure exerted by the tension of the wire. It is a characteristic feature of the invention that the wire 23, between the guide rolls 25 and 27, is supported only by another wire 37 and therefore is not compulsorily guided in a predetermined arc. The arc denited States Patent 0 3,235,724 Patented Feb. 22, 1966 scribed by the wires 23 and 37 is self-adjusting, i.e. the distance between the wire 23 and the felt 15 is determined by the pressure from the wires and the counter pressure from the fibre suspension or the web 53. The water removed from the web 53, formed between the felt 15 and the wire 23, mainly flows through the wires 23 and 37. The felt 15 is only insignificantly wetted and very little water will enter the perforated drum 12. The wire 23 is preferably a fine mesh, e.g. of plastic, that leaves very little marking on the formed web 53. To enable a higher pressure to be exerted against the web 53 and the felt 15, the supporting wire 37 is stronger and preferably made of metal. The endless wire 37 forms a loop around the rolls 25, 27, 39 and 43. A tension roll 41 is vertically adjustable to give the necessary tension of the wire 37.

The drum 12 is provided with an internal stationary box 45 whose walls are sliding against the inner surface of the perforated periphery 11. The box 45 is divided into three separated zones 47, 49 and 51. The zone 47 is located opposite that part of the web forming wire 23 where the web 53 has become comparatively solid and the task of this zone 47 is to supply compressed air to be blown through the perforated drum periphery 11, the felt 15, the web 53 and the wires 23 and 37 in order to increase the dryness of the web 53. Alternatively the zone 47 may be used as a suction box sucking air through the Web 53 in the opposite direction. The zone 49 is located opposite and extends after the nip between the roll 27 and the drum 12 and is kept under high vacuum to insure that the web 53 after the nip will follow the felt 15 and not the wire 23 which is carried downwards over the roll 27. The zone 49 also works as a suction box drying the web 53 by sucking air and moisture from the web 53 into the felt 15.

A solid press roll 55, which may be provided with a rubber covering is arranged to form a nip with the drum 12 after the guide roll 27 and removes the web 53 from the felt 15. The zone 51 of the internal stationary box 45 is located just before and ends at the nip between the drum 12 and the press roll 55. The zone 51 is maintained under a moderate vacuum and the paper web 53 can therefore easily be transferred to the press roll 55 on which it can be further pressed or transferred for further drying.

The described methods and the apparatus shown on the drawing are examples which easily can be modified in details, e.g. the web may be further dewatered while on the felt 15 by means of further one or more press rolls between the rolls 27 and 55. Another modification might be to vary the pressure exerted on the web by the mesh by using further supporting wires acting at different positions and with different tensions.

I claim:

1. Apparatus for forming a web of fibrous material comprising, a rotatable fluid permeable drum, an endless fluid permeable web extending about a portion of the perimeter of said drum and in contact therewith, an endless fine mesh screen belt extending about a part of said portion of the drum perimeter and defining a web-forming space with said permeable web, said permeable web and screen belt movable in coordination with rotation of said drum, said screen belt leaving the perimeter of said drum at a first point, and said permeable web leaving the perimeter of said drum at a second point spaced from said first point in the direction of rotation, means for supplying a slurry of fibrous material to the web forming space defined between said permeable web and said screen belt, and means for pressing the fibrous web formed in said forming space against said permeable web and said drum between said first and second points.

2. Apparatus for forming a web of fibrous material comprising, a rotatable fluid permeable drum, an endless fluid permeable web extending about a portion of the perimeter of said drum and in contact therewith, an endless fine mesh screen belt extending about a part of said portion of the drum perimeter, and a second heavy screen belt extending about said part of said portion of the drum perimeter and disposed outwardly of said fine mesh screen belt, said belts defining with said permeable web a web forming space.

3. Apparatus for forming a web of fibrous material,

comprising a fluid permeable rotatable drum, an endless fluid permeable web extending about a portion of the perimeter of said drum and in contact therewith, an endless screen belt extending about a part of said portion of the drum perimeter and defining a web forming space with said permeable web, said web and screen belt movable in coordination with the rotation of said drum, said screen belt leaving the perimeter of said drum at a first point and said permeable web leaving the perimeter of said drum at a second point spaced from said first point in the direction of rotation of said drum, means for supplying a slurry of fibrous material to the web forming space, means in said drum for supplying air flow through the fibrous web to facilitate removal of moisture therefrom as it passes along said part of the drum perimeter, and means in said drum between said first and second points to draw air through the fibrous web to withdraw moisture therefrom.

4. Apparatus for forming a web of fibrous material, comprising a fluid permeable rotatable drum, an endless fluid permeable web extending about a portion of the perimeter of said drum and in contact therewith, an endless screen belt extending about a part of said portion of the drum perimeter and defining a web forming space with said permeable web, said web and screen belt movable in coordination with the rotation of said drum, said screen belt leaving the perimeter of said drum at a first point, and said permeable web leaving the perimeter of said drum at a second point spaced from said first point in the direction of rotation thereof, means for supplying a slurry of fibrous material to j the web forming space, means in said drum for supplying air-flow through said fibrous web therefrom along said part of the drum perimeter, and means between said first and second points and within said drum for drawing air through said fibrous web to withdraw moisture therefrom, said air drawing means including a first vacuum chamber adjacent said first point for applying a high vacuum to the fibrous web and a second vacuum chamber adjacent said second point for applying a lower vacuum to the fibrous web.

5. Apparatus for forming a Web of fibrous material,

comprising a fluid permeable rotatable drum, an endless fluid permeable smooth felt web extending about a portion of the perimeter of said drum and in contact therewith, an endless fine mesh screen belt extending about a part of said portion of the drum perimeter and defining a web forming space with said felt web, an endless heavy screen belt extending outwardly of and along with said fine mesh belt about said part of the drum perimeter, said felt web and screen belts movable in coordination with rotation of said drum, said screen belts leaving the perimeter of said drums at a first point, and said felt web leaving the drum perimeter at a second point spaced from said first point in the direction of rotation of said drum, means for supplying a slurry of fibrous material to the web forming space, and roll means between said first and second points for pressing the fibrous web formed in said forming space against said felt web after said screen belts have left the perimeter of the rotatable drum.

6. Apparatus as claimed in claim 5 further comprising means facilitating the withdrawal of moisture from the fibrous web, said means including a first air-flow chamber within said part of the drum perimeter and adjacent said first point, a first vacuum chamber adjacent said first chamber and extending toward said second point and arranged to facilitate high vacuum withdrawal of moisture from said fibrous web, and a second vacuum chamber adjacent said second chamber and disposed generally inwardly of said pressure roll means and arranged to facilitate low vacuum withdrawal of the moisture from said fibrous web.

References Cited by the Examiner UNITED STATES PATENTS 1,875,075 8/1932 Mason 162203 2,174,744 10/1939 Hill 162370 2,581,210 1/1952 Simpson 162-3l8 2,995,186 8/1961 De Montigny 1623 17 3,056,719 10/ 1962 Webster 1623 1 8 3,057,402 10/1962 Webster 162-318 FOREIGN PATENTS 316,224 10/ 1930 Great Britain. 614,901 2/1961 Canada.

OTHER REFERENCES Engel: Toiles en Matieres Plastiques Pour Presse- Pate, La Papeterie, November 1958, pp. 811, 813, 815.

DONALL H. SYLVESTER, Primary Examiner.

MORRIS O. WOLK, Examiner, 

2. APPARATUS FOR FORMING A WEB OF FIBROUS MATERIAL COMPRISING, A ROTATABLE FLUID PERMEABLE DRUM, AN ENDLESS FLUID PERMEABLE WEB EXTENDING ABOUT A PORTION OF THE PERIMETER OF SAID DRUM AND IN CONTACT THEREWITH, AN ENDLESS FINE MESH SCREEN BELT EXTENDING ABOUT A PART OF SAID PORTION OF THE DRUM PERIMETER, AND A SECOND HEAVY SCREEN 